Director of National Intelligence James Clapper, second from right, listens on Capitol Hill in Washington, Wednesday, Jan. 29, 2014, while testifying before the Senate Intelligence Committee hearing on current and projected national security threats against the US. From left are, Defense Intelligence Agency Director Lt. Gen. Michael Flynn, CIA Director John Brennan, Clapper and FBI Director James Comey. (AP Photo/Pablo Martinez Monsivais)

WASHINGTON (AP) — The Syrian militant group tied to al-Qaida, the al-Nusra Front, wants to attack the United States and is training a growing cadre of fighters from Europe, the Mideast and even the U.S., the top U.S. intelligence official told Congress on Wednesday.

Director of National Intelligence James Clapper told the Senate Intelligence Committee that such al-Qaida groups in Syria have started training camps “to train people to go back to their countries” — one of the newest threats emerging in the past year to U.S. security. He said “al-Nusra Front, to name one …. does have aspirations for attacks on the homeland.” Clapper didn’t elaborate or offer any evidence of al-Nusra’s desire to attack the U.S.

Clapper described the Syrian militants as one of the newest groups to join a diverse and widely dispersed network of al-Qaida-affiliated and other extremists bent on carrying out attacks in the U.S. He said more established groups like Yemen’s al-Qaida in the Arabian Peninsula are still more capable of carrying out attacks against the U.S., but described steep growth in numbers of fighters in Syria.

Clapper said out of an estimated 75,000 to 110,000 rebels overall battling the government of Bashar Assad in Syria, some 26,000 are extremists, and about 7,000 of them foreigners from some 50 countries, including Europe.

“Not only are fighters being drawn to Syria, but so are technologies and techniques that pose particular problems to our defenses,” said committee chairwoman Dianne Feinstein. She warned Syria could become “a launching point or way station for terrorists seeking to attack the United States or other nations,” in the annual hearing Wednesday to hear the U.S. intelligence committee’s assessment of worldwide threats.

U.S. intelligence officials have said a handful of American foreign fighters, and hundreds of European militants have already returned to their home countries. The officials spoke on condition of anonymity because they were not authorized to speak publicly on the topic.

The extremist fighters belong mainly to two major groups, Islamic State of Iraq and the Levant and Jabat al-Nusra — both allied with al-Qaida. The State Department has no estimates of how many Americans have gone to fight with Syrian rebels, but British defense consultant IHS Jane’s puts it at a few dozen. An estimated 1,200 to 1,700 Europeans are among rebel forces in Syria, according to government estimates.

U.S. analysts fear more of those militants will tire of the battle against Assad, whose government shows no signs of collapsing, and they will take their newly acquired, battlefield-honed terrorist skills back to Europe or the U.S., where even a small bomb in a shopping mall can grab much greater headlines than the now-routine reports of car bombs in Syrian cities.

The continued threat to U.S. interests from the al-Qaida brand also shows that though weakened after the 2011 killing of terrorist leader Osama bin Laden in Pakistan, the group is proving resilient.

“They’ve gone to school us, on how we try to track them,” he said. “So the combination of …the geographic dispersal and the increasing challenges in collecting against them, makes Al Qaida, in all of its forms, a very — in total, a very formidable threat.”

Still, U.S. intelligence analysts say core al-Qaida leader Ayman Al-Zawahri and his lieutenants are too preoccupied by the constant threat of U.S. drone strikes to plot 9/11-style attacks, so Zawahri has empowered the various “nodes” of his organization to choose their own, often local targets, though he encourages them to focus on the “far enemy” of the U.S. when they can.

U.S. intelligence officials say Zawahri so far has not called on the Syrian branches to attack U.S. targets, allowing them to focus on the war against Assad.